Normally, cigarettes are manufactured to be wholly consumed by the smoker once lit. When smoking such cigarettes, the smoker takes a number of puffs on the cigarette. For most smokers, smoking of a single cigarette with around 7 to 12 puffs, depending on the tobacco rod length, provides the desired smoking pleasure.
A prior art patent search has been effected with respect to the subject matter of this application and, as a result, the following United States patents have been located as potentially-relevant prior art:
______________________________________ 4,319,587 4,893,638 4,328,817 4,924,888 4,452,259 5,033,484 4,637,410 5,072,743 4,739,775 5,105,839 4,838,286 ______________________________________
In addition, the following prior art has been drawn to the applicants attention:
______________________________________ U.K. 2,063,050 U.K. 2,149,287 U.K. 2,175,789 E.P. 0,365,882 ______________________________________
Of this prior art, U.K. 2,149,287 is equivalent to U.S. Pat. No. 4,838,286 cited above, U.K. 2,175,789 is equivalent to U.S. Pat. No. 4,893,638 cited above and U.K. 2,063,050 is equivalent to U.S. Pat. No. 4,328,817 cited above.
Certain of this prior art discloses attempts to provide cigarettes which are intended to be consumed for part of the tobacco rod, extinguished and relit, as described, for example, in U.S. Pat. Nos. 4,319,587, 4,452,259, 4,739,775 and 5,072,743. However, such cigarettes otherwise are conventional in character. A variety of parameters which are conventional in cigarettes are described, for example, in U.S. Pat. Nos. 4,924,888, 5,033,484 and 5,105,839, although such references describe various manipulations to achieve the effects described therein.
U.S. Pat. Nos. 4,637,410 and 4,893,638 describe cigarettes which have a smaller-than-normal circumference to provide a slim cigarette appearance. U.S. Pat. No. 4,893,638 describes employment of a very high packing density for tobacco in a filler rod of ground tobacco.
None of the patent prior art referred to above discloses or suggests the provision of the actual combination of parameters described below which enables the provision of a cigarette having a greater-than-normal number of puffs.
The applicants are aware of unfiltered cigarettes made in Russia and known as "Papirossy", which employ a high density of tobacco in a relatively-short tobacco rod and which exhibit a low burn rate, which might be expected to lead to a high number of puffs. However, such cigarettes self-extinguish under the standard smoking conditions described below.
As described below, the various smoking parameters, including puff count for a cigarette, are determined according to the current tobacco industry standards in effect at the time of filing this application. Certain of these standards have changed with time and the standard in effect in 1957 for determining puff count is described in an article by Keith et al. entitled "Characteristic Studies on Cigarette Smoke" Tobacco Science, 1957, pp. 51 to 57. When a conventional cigarette and cigarettes constructed in accordance with the invention were smoked according to the two procedures, namely the current standard smoking procedure (ISO) and the former standard smoking procedure, then the puff count which resulted from using the current standard was, on average, 67% of the puff count which resulted from using the former standard.
The data presented in the Keith et al. article indicates that, on average, 12 puffs (determined at the standard described therein) were obtained for 40.2 mm smoked length (i.e. 29.8 mm butt length from a 70 mm cigarette length) of an unfiltered cigarette. By applying the 67% ratio referred to above, the 12 puffs translates into 8.04 ISO puffs for 40.2 mm smoked length, which converts to 9.4 ISO puffs for 47 mm smoked tobacco rod length (the ISO standard for a filter cigarette of 55 mm tobacco rod length). The ISO puff count corresponds to a linear burn rate (as the term is defined below) of 5.0 mm/min, a value greater than the maximum value described herein.
A prior attempt has been made to provide a slower burning cigarette with more puffs per cigarette. In this regard, "Camel" brand cigarettes, available in the United States in the late 1930's and early 1940's, were advertised as containing a greater tobacco weight than then-conventional cigarettes and as being a slower burning cigarette which gives a 25% greater number of puffs than a conventional cigarette.
If the comparison made in the "Camel" cigarette advertising is considered in terms of the smoking data provided by Keith et al., then the 25% more puffs referred to in the advertising materials corresponds to 11.75 ISO puffs for the "Camel" cigarettes. As described in more detail below, the cigarettes of the invention have a greater number of puffs than those for the "Camel" cigarettes.
The applicants are aware of an advertisement from 1952, claiming that an unfiltered cigarette having the brand name "Pall Mall", available in the United States, has 17 puffs. The advertisement compares a cigarette having an approximately 85 mm rod length for the "Pall Mall" cigarette with a 70 mm rod length for the conventional cigarette. The longer "Pall Mall" cigarette is indicated to have the same 17 puff count as the normal-length cigarette. However, no manner of determining the number of puffs described in the advertisement is specified but, since the number is indicated to be that for a conventional cigarette, the stated number of puffs would seem to have been determined in a manner different from the procedure described in the Keith et al. article, which would indicate that the "Pall Mall" cigarette possessed no more than 14 puffs for 47 mm smoked length, as determined by the older standard and hence no more than 9.4 puffs by the current standard. In fact, historical data indicated that this "Pall Mall" cigarette had 8.5 ISO puffs for a 47 mm smoked length.
Neither of these prior art cigarettes, i.e. the "Camel" and "Pall Mall" cigarettes, was intended to be consumed other than at one time, in contrast to the present invention, in which the novel cigarettes are intended to be smoked, extinguished and relit for a second smoking at a subsequent time. These prior art cigarettes are considered to be "conventional", as the term is employed herein, as being a cigarette regularly-available in the market-place at the relevant time.
The applicants also suspect that perhaps some so-called "roll-your-own" smokers, that is, persons who make for themselves at home or the like cigarettes from papers or tubes and loose tobacco, may have on occasion achieved sufficiently high tobacco densities as to provide a large number of puffs. However, such cigarettes have a significant variability of parameters not evident in a factory-made cigarette and it is not possible to obtain such cigarettes in order to ascertain their burn characteristics under the existing standard smoking conditions, in particular, whether such cigarettes may self-extinguish.
In connection with the establishment of the parameters defined below for the novel cigarette described herein, several characteristics of commercial cigarettes have been considered, particularly for cigarettes available on the Canadian market over the past 24 years, including puff count, linear burn rate and free burn rate (as the terms are defined below), and, of all the cigarettes considered, the slowest burning commercial cigarette exhibited a linear burn rate of 4.43 mm/min. and a free burn rate of 4.2 mm/min., both values greater than the maximum values employed herein for the novel cigarettes of the invention. This commercial cigarette exhibits a standard number of puffs, namely 10.6 for a 55 mm tobacco rod length, but employs a very high level of ventilation of 68%, which accounts for the closeness of the linear and free burn rate values.
As will be seen from the description below, one parameter which is employed in providing the novel cigarette of the invention is the employment of a density of tobacco higher than that conventionally employed in commercial cigarettes. The employment of such higher density herein is the reverse of a trend by the cigarette industry over many years to find ways to decrease the weight of tobacco contained in cigarettes. One problem that employment of a higher density of tobacco produces is a corresponding increase in draw resistance. As will be seen from the detailed description of this invention, the problem of increased draw resistance has been overcome by employing a particular type of blend of tobacco in the rod.